it's true.
An event horizon is a theoretical sphere surrounding a black hole, beyond which objects pass into oblivion.
A black hole by theoretical definition is so dense that nothing, not even light, can escape its gravitational clutches once trapped inside.
These black holes are generally said to be active, consuming matter voraciously, through a process called accretion, and converting some of this matter to X-rays and other radiation that signal their presence.
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